To extend knowledge on the regulation and the functions of sleep in health and disease, this study will investigate the effect of the antidepressant phenelzine (Nardil) for at least 5 weeks in patients with major depression. Effect on mood, memory, polygraphic sleep measures, the sleep EEG, circadian phase position (assessed by neuroendocrine measures melatonin, ACTH, cortisol and body temperature) and dream recall will be assessed.